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What are the design disadvantages of a monowheel landing gear setup which might have led to its historic rejection?
Monowheels have a lot to be said for them, which is why we use them in gliders. They save weight, drag, and cost, are tolerant of tire failures, and frequently handle outlandings with aplomb.
However, they have not proven to be popular outside of gliders. There are very few examples of them, with only the Europa XS, the B-52, and the U-2 as modern(-ish) examples I can think of. (And even the Europa XS sales have now shifted largely over to tricycle gear.)
Below is a monowheel variant of the Europa XS:

And here's a landing B-52 (technically not a monowheel, but still a centerline gear configuration), with the outrigger supporting the starboard wing:

While it can be argued that maybe the relative absence of monowheels is because pilots are a conservative sort and will only fly things that "look right", that's a less compelling argument when someone says "your job is on the line". If the monowheel were better for a broad class of planes, the logical conclusion is that there would be commercial pressures which would lead to their broader introduction.
(This would have been especially true in wartime 1940s when rubber was notoriously hard to come by and minimizing the number of tires would have had instant payoff.)
Perhaps the technology to enable monowheels' theoretical superiority wasn't (and still isn't?) present? With the exception of gliders, outriggers are necessary, and those would be dramatically smaller and less draggy with modern composites as opposed to, say, chunks of wood or steel.
Anyone have any hard data on this? Surely NASA, or NACA, or some early airplane manufacturer must have dabbled in this and written down their findings...

The U-2 was specialized for one and only one purpose, so its landings are not great examples of successful or failed gear topologies, but boy is this video fun: https://youtu.be/eamnTyfkUBY?si=bD__Gj58ftYYTQGu&t=70

B52 is definitely not a monowheel, it has 4 main landing gears (each with two tires) and 2 on the wing tips.

@sophit yes, see my comment in response to your answer. It's possibly a scaling concern. However, it embraces the monowheel approach, where the main wheels are close together that it is not fully stable while on the ground, and needs outriggers to support the wings.

Building on your point, if we define "monowheel" as anything which requires outriggers (and maybe this isn't a fair and reasonable definition), there are a wide variety of "monowheel" configurations, incl. main-and-tailwheel (most gliders), main-and-nose-and-tailwheel (ASK21), bicycle (Harrier), quad truck (B52), and maybe more?

The monowheel question was pretty much answered by @sophit (unless you disagree), so by continuing the discussion it seems that you are expanding the question to bicycle landing gear. Which is fine but you may want to clarify that in the question. If I am reading into your question and comments correctly, while currently there may be practical reasons for tricycle landing gear over bicycle, your question is if future technology allowed it, would bicycle landing gear possibly become a thing, is that right?. I'm thinking of the Segway, a design that required new technology to make it work.

@StevePemberton see my definition of "monowheel". If there's a better word to catch all the configurations which require outrunners, lemme know and I'll update the question. Re your question, I'm mostly just curious why something which seems simpler and more robust, wasn't actually. (I'm assuming that if monowheels had been awesome solutions, we would have many of them out there.) This could possibly be because of continuing issues with it; or because during the period of rapid innovation (through the 1940s?) the tech didn't exist to overcome some key obstacle.

@StevePemberton I would not say that sophit has answered the question. You can see my comment on his answer, but in short while it gives some specific insight into massive jetliners, there is a wide range of designs which exist between gliders and jetliners. And, yet, vanishingly few use a monowheel/tandem/bicycle topology.

Thanks for adding the photo.  That looks like a prop strike waiting to happen though!

@MichaelHall I thought so, too. Doesn't look so bad from this angle, though: https://www.airliners.net/photo/untitled/europa-xs-monowheel/1681781 And the tricycle variant doesn't seem to have any additional clearance: https://th.bing.com/th/id/R.e5cdc62de26d6acc2f49087b2af0cca6?rik=j%2fxZIeTohPDsZQ&pid=ImgRaw&r=0

KennSebesta - I think I see what you are saying. Tail-dragger and tricycle gear have side-by-side main landing gear bogies. They may also have additional center gear under the fuselage (MD-11). You are describing planes with center main landing gear only. In some cases monowheel ( Europa XS), in other cases two-wheel center bogie (U-2), in other cases tandem center bogies (B-47).  I think the B-52 may not be a good example however because even though it has bicycle main gear and outriggers and visually has a "centered" look, it does not have center gear, only side-by-side main gear bogies.

@StevePemberton is monowheel perhaps the wrong way to describe this? Maybe "centerline" is better, since the concept is that there are planes which will prone to tipping onto a wing in typical wind conditions, and planes which will not. Those which are then either have outriggers (Europa, U-2, B-47, B-52), or skids (gliders) to protect the wing.

KennSebesta - centerline might be good, defined as one or more landing gear struts centered under the fuselage, with no side-by-side struts. I don't think I would include outriggers in the definition as those are merely technical solutions that deal with stability.  The AN-124 landing gear for example has a lot of similarity with the B-52, however because of its wider fuselage it does not require outriggers.

B52s are most certainly stable on the 4 main trucks. The outrigger gear on the wing tips is not for stability, it is to keep the wing tips from dragging on the ground. The wings of the B52 are very flexible. As they contain large fuel tanks, when the tanks are full, the wings droop considerably. When the tanks are nearly empty, the wings lift and the outrigger gear will be several feet in the air.

@Jim fascinating! Do you have a background link on that? I went looking and found this picture, which presumably is from a landing: https://i.sstatic.net/lDaDV.jpg. Pretty clearly, that outrigger is keeping the starboard wing from dragging, while the port wing is extremely elevated.

@KennSebesta I worked maintenance on B52G while I was in the USAF. whenever the wing fuel tanks were low or empty, the wing would raise up and the outrigger would be off the ground. in fact if the wind was variable, gusting, the wing would move up and down. very annoying if you were working on it. most of the time we kept fuel min the wing tanks to prevent this. That is why most pictures will show the gar on the ground.

If an A380 landed on one wheel only it would leave a groove so deep that the runway should be rebuilt after every landing.
A standard civil tarmac runway can sustain tires with a maximum inflation pressure of 7-8 bar (100-120 psi - a tarmac runway couldn't survive a Grand Tour race ). On grass the maximum pressure might be half of that value. Multiplying this maximum inflation pressure by the footprint area of the tire we get the maximum weight that each tire can bear before ruining the landing strip. Given the total weight of the aircraft, we can then decide to spread it either on few big wheels (one single wheel as an extreme case) or many small wheels.
For a jetliner the second option (many small wheels) is the preferred one due to several reasons:

it gives a more compact design for the landing gears;
the design is redundant; should one wheel get damaged the other ones can sustain its share of weight without damages;
smaller wheel implies less inertia to start rotating at touchdown;
they can be inflated at a lower pressure increasing their life.

Just for fun, let's see what tire our monowheel A380 would need. According to this NASA report, the footprint area $A_p$ of a tire can be estimated via the following empirical equation:
$A_p=0.45d²$
where $d$ is the nominal diameter (in inches). This is the equation 12 in the report with the additional assumptions that under load the tire gets squashed of 1/3 of its diameter and that its width to diameter ratio is 1/3 too.
Using the maximum 120psi allowed for a civil landing strip and the 1'200'000lbf of an A380 we get:
$A_p=1'200'000/120=10'000=0.45d² \Rightarrow d=150 in$
Well, a very big wheel indeed!

Technically, an A380 could still land on only one wheel, you'd just need to make it very very large

@MikeB: it would be more practical to simply slide on the belly

@sophit, that's an excellent point about scaling effects. Building on your point, the B52 isn't a true monowheel, since it has a series of wheels narrowly grouped together. However, a single main wheel seems to be compatible for lightweight GA and even the U2, so scaling effects alone cannot be the cause. Do you have any data about where the crossover point is, where a wide enough, tall enough tire would no longer fit into the airplane? As you point out, gliders are light enough not to have an issue, and so presumably are many (most?) GA airplanes.

I think the "cross-over point" is roughly the U2. Is there anything larger that's configured with true bicycle gear? As noted several times, the B52 is not bicycle gear - it's got 4 main gear that just happen to be mounted close together and attached to the fuselage.

Even the U2 doesn't use a single wheel - both the fore and aft undercarriage has two tyres side by side

@sophit, I see where you're going with this, but, based on the data given, your conclusion "In general for an aircraft heavier than a glider, monowheel is something impractical." is a bridge too far. My question was for all non-gliders, but this answer is specific only to jetliners. There are many, many great design choices which wouldn't work on jetliners, such as single engine piston propulsion, unpressurized cabins, single tires on each main, floats, tailwheel etc... So no argument for why monowheels wouldn't work on jetliners, but what about the "everything else"?

@sophit thanks for the changing that part, and I really appreciate the worked example for the A380 tire. Is MTOW on a jetliner a fair approximation for maximum force on landing, or would it need to be higher to accommodate for rough landings? BTW, here's a 108" dia tire on a US prototype bomber: https://www.sim-outhouse.com/sohforums/showthread.php/31195-Bristol-100-ton-bomber?s=ca565feee69d4046b6845cddc400de7b&p=355274&viewfull=1#post355274 I wonder if we can get DALL-E to do some concept art of what that A380 would look like with a monowheel? :D

I'm gonna call bullshit on tarmac not surviving a Grand Tour event...

If that was intended as a joke, then yes

@Jpe61: done

150" isn't that large - mining truck tires reach that size. It's other impracticalities that make it pointless and dangerous.

There are some serious show stoppers before you even get started.
The biggest problem for monowheels is, if you want minimalist outriggers near the wing tips to really gain the drag or structural benefit of a single main wheel, you you need a maneuvering path that is wider than the plane's wingspan. And even if you do find a taxiway that is wide enough, unless it's WAY wider, you need a center line to follow to avoid driving your outriggers into the weeds.
And if you move the outriggers inboard to make it able to operate from narrow taxiways, they have to be much more robust, and you are creeping toward regular landing gear now, except you have three units, one big middle one, and two smaller ones outboard. Might as well do it the regular way and do away with those hassles, which is the reason almost nobody does that configuration outside specialized cases.

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not proven to be popular outside of gliders

The reason may be the ability to land and take off from less than ideal surfaces.
Two strong wheels and a tail-skid was the norm for the first 50 years of aviation.  Many "airfields" of this time were little more than closely cropped stretches of grass.
Paved runways opened the door to not only monowheels, but also nose wheels.  But weakly designed landing gear simply won't cut it out in undeveloped areas, where a mechanical breakdown means you're stranded.
Two main wheels also offer the possibility of differential braking to improve ground control.

That's an interesting point about ground control. Maybe after much experimentation there was no satisfactory manner to steer on the ground without either a short-coupled nosewheel or two wheels with differential braking?

Taxiing a mono wheel in a cross wind may not be easy, but a weight savings of 100 lbs is of interest.


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Are there guidelines for how rudder pedals should be shaped?
I've seen a lot of rudder pedal design, from simple welded steel tubes to more complex branded aluminum forgings.
They all seem to work equally well in my experience, and I've never found myself wishing an airplane's pedals were a different shape.
However, there must be designs which work better and designs which work worse. Considering how common and uniform flight sticks and yokes are, I'm surprised there isn't more manufacturer consensus on pedal shape. The upshot from the lack of design consensus is it's hard to design through emulation. Maybe ACA did a bang-up job with the Citabria's rudder pedals, or maybe they grabbed something easy to  manufacture in the 1950s and it was grandfathered in despite glaring deficiencies.
Is there a resource which could be used to make an informed choice for rudder pedal shape, e.g. a study of rudder pedal shapes vs. performance and user comfort?
P.S. For info, What are specified rudder pedal forces? gives some data for the forces they should be able to take.

Are you talking about the rudder pedal or foot rests? Many large transports have separate foot rests since they are flown on autopilot most of the time.

@user71659 I had it in my mind somehow that "foot rest" that was the official name, but seeing your post I see where that is likely incorrect. I've clarified the question to make it clear I'm asking about the pedals in normal small GA craft.

@KennSebesta Much clearer now, thanks!

A couple of observations-- one, it's not surprising that manufacturers would end up making different choices in optimizing the shape of the rudder pedals in aircraft where each rudder pedal also activates the wheel brake on that side (eg your second embedded link), than in aircraft where the rudder pedals have no braking function (eg your first embedded link).  To control the rudder and brake independently, each pedal must have two degrees of freedom of motion, not one.  And two, the amount of physical space available in the nose of that sailplane (in your first embedded link) is very limited!

PS perhaps I'm making an incorrect assumption in thinking the Citabria in your second embedded link has toe brakes (activated by the pedals) rather than heel brakes (activated by something on the floor).  It's hard to tell from the photo.  Here's some interesting reading that pertains somewhat to why rudder pedal shape might be important: https://backcountrypilot.org/forum/do-shoes-matter-25495?start=40

@quietflyer almost all Citabrias have toe brakes. The heel brakes, from what I remember, where discontinued early on in the production run.

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What are these four tubes for in the intake for an Extra 300?
The fuel-injected engine has six cylinders, so it's not a "per-cylinder" thing nor is it related to a carburetor.

P.S. That screen is the entirety of the air filter. Apparently it's meant to keep out small birds, and not much else.

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How does this total energy compensation pitot tube work?
This is a pitot tube I saw on a glider:

The far right end plugs into a receiver. The far left end has the RAM port at the tip, the static ports just behind it, drilled in laterally, and a venturi hanging down below.
There's some kind of what looks like acid etching on the tip, terminating just behind the static ports.
Something similar can be seen at https://www.esa-systems.com/en/products/details/total-energy-probe-brst-840-mm-1/, where they mention "The TE – measuring head is based on the long established Venturi nozzle principle."
From other things I've read, I had the understanding that TEC calculations required a pressure measurement in the lee of a round surface. This seems to be a little different here. How is this probe working? What does the venturi do?
P.S. I'd love a mathematical description.

Related, but not a duplicate : How does an energy variometer work?

The pitot tube here does not do anything special- it's simply a pitot tube, static port, and venturi all combined in one instrument. It delivers these three pressures to the pressure instruments from three separate ports. The part that plugs into the aircraft looks something like this:

From there, the pressures can be used to drive a normal airspeed indicator, total energy compensated variometer, or any other pressure instruments.
The excellent answer here describes how a backwards-facing pitot probe can be used to make a total energy measurement. Facing a pitot tube backwards negates the value of the measured pressure- it turns $\frac{1}{2}\rho v^2$ into $-\frac{1}{2}\rho v^2$, i.e. a suction. It just so happens that a venturi tube also creates a suction proportional to $\rho v^2$, so a venturi tube can be used in lieu of a backwards facing pitot tube to accomplish the same measurement.
Specifically, the pressure in drop in a venturi tube is given by $ P_s-P_v=\frac{\rho}{2}(v_2^2-v_1^2) $, where $v_1$ is the true airspeed and $v_2$ is the speed of the air in the venturi tube. $P_s$ is the pressure at the opening (i.e. the static pressure) and $P_v$ is the pressure as measured by the venturi tube.
Assuming incompressible flow (which is a good approximation for so long as the flow is sufficiently subsonic), $A_2v_2=A_1v_1$, where $A_1$ and $A_2$ denote the cross-sectional areas of the mouth of the venturi and its narrowest point, respectively.
Putting this together, the venturi pressure is given by:
$$ P_v = P_s - \frac{\rho v_1^2}{2}\left(\frac{A_1^2}{A_2^2}-1\right) $$
If $A_1/A_2$ is chosen to be $\sqrt2$, this equation is identical to the one in the linked answer, and so works identically to a backwards-facing pitot tube in measuring total energy.

Neat. Do you happen to know the relative advantages of using a venturi vs. a backwards ram tube? And why does the OD of the venturi flare out in the pictured probe?

@KennSebesta One obvious advantage is that reduces the total number of tubes needed, and it can be placed in relatively undisturbed air. Obviously, it's impossible to place anything backwards facing in totally undisturbed air.

I'm not 100% sure why the lip flares out, but my guess is that a sharp edge would create interference and disturb the measurement.


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Can such an aircraft take off vertically?

The compressor ejects compressed air from the gap at high speed.  The red arrow represents the path of compressed air.  It is lift that adjusts the speed of the compressed air to adjust the aircraft.

Have you make reshearch?

@L'aviateur How does VZ-9 blow compressed air on its upper surface?

They realized that this physical phenomenon(coanda effect) could be used on his device to produce a more practical VTOL device. The flow should instead exit from the top of the device and be redirected downwards by a device similar to shutters.
This mechanism should produce a lift all around the device allowing him to land flat and no longer standing as in Project Y

https://lh3.googleusercontent.com/proxy/GR7P0QjuUNu08nRtAExnYJkfFqSuKm3AnfeBjX6hyiyanhjkhA0cpk1ja7TZe8cujJtBKkLyKz8GN-PDNgaa-DgkEvlQn31EpVTJFrcuZoaCyQ

@L'aviateur Air must be ejected at high speed, otherwise the lift is not enough.

This us the Avro-Canada VZ-9 .He focused on the " Coanda  " effect  capable of flying a possible flying saucer.

A.V. Roe (Avro) Aircraft Limited (later Avro Canada) based its design concept for the Avrocar on using the exhaust from turbojet engines to drive a circular “turborotor” which produced thrust. By directing this thrust downward, the turborotor would create a cushion of air (also known as “ground effect”) upon which the aircraft would float at low altitude. When the thrust was directed toward the rear, the aircraft would accelerate and gain altitude.
Each service had different requirements: the Army wanted to use it as a subsonic, all-terrain troop transport and reconnaissance craft, but the USAF wanted a VTOL aircraft that could hover below enemy radar then zoom up to supersonic speed. Avro’s designers believed they could satisfy both services, but these two sets of requirements differed too much.
Research data originally indicated that a circular wing might satisfy both the Army’s and Air Force’s requirements, and Avro built two small test vehicles to prove the concept.

Designated the VZ-9AV Avrocar (“VZ” stood for “experimental vertical flight,” “9” for the ninth concept proposal, and “AV” for Avro).

Tests with scale models at Wright-Patterson AFB, Ohio, indicated that the cushion of air under the Avrocar would become unstable just a few feet off the ground. The aircraft would be incapable of reaching supersonic speeds, but the testing went ahead to determine if a suitable aircraft could be developed for the Army. The first prototype was sent to NASA. There, wind tunnel tests proved that the aircraft had insufficient control for high speed flight and was aerodynamically unstable.The second Avrocar prototype underwent flight tests that validated the wind tunnel tests. If it flew more than three feet above the ground, the Avrocar displayed uncontrollable pitch and roll motions, which the Avro engineers called "hubcapping." The Avrocar could only reach a maximum speed of 35 mph, and all attempts to end the hubcapping failed. The project was cancelled in December 1961.

Edit: The 124-blade "turborotor" was placed in the center with the majority of the thrust flow directed straight down through an opening in the floor. Part of this flow was separated and redirected to operate the control system which ran around the outer periphery of the disc. Power for the rotor was generated by three reactors attached to the main structure. Each engine had its own fuel and oil tanks.
The thrust deflection control system consisted of a large ring located around the main disc, with the flat part inside. The pilot's controls moved the ring in relation to the rest of the aircraft, affecting the air flow. The vertical lift could be increased by lowering the ring entirely. Tilting the ring resulted in asymmetric thrust for directional control.
Source :https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195801/avro-canada-vz-9av-avrocar/

So nothing is impossible but this concept turns out to be complex

The stability issues could be solved with a computer controller. Time to revive avrocar?

good idea Maybe yes.

but what would it be able to do that current aircraft and helicopters can't? The hovercraft has gone almost extinct because its niche is just too small to sustain an industry.

Yes this is a experimental aircraft :Although American public opinion lived in disproportionate fear of flying saucers, the US Army and the US Air Force teamed up to launch a program to study the flight possibilities of flying saucers , officially called "aircraft to lenticular wing so they search if it is better than aircraft and helicopter.this is the goal of experimental aircraft s

@JohnDvorak The speed and direction of compressed air must be controlled by the computer.

They use the ground effect, but mine is not.

Your use it.there is no one which "fly"


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The wing has a pressure gradient along the AB direction, is there a pressure gradient along the CD direction?
The wing has a pressure gradient along the AB direction, is there a pressure gradient along the CD direction?

It's called "lift", isn't it?

Because of the low surface pressure, there is a normal pressure gradient.

Yes, but a weaker one than in lengthwise direction.
You can observe the local pressure by comparing the distance between two stream lines. When they move closer together, speed goes up and static pressure goes down. As you move away from the airfoil, the distance between stream lines recovers to its value at infinity.

Stream lines around airfoil (picture source).
This effect depends on the Mach number of the flow. At very low speed, the recovery is rather quick because speeding up contracts the airflow so it is easy to make way for the airfoil. At higher (but still subsonic) speed, speeding up is coupled with a drop in density, so the contraction is less pronounced and it takes more height for the disturbance to die down. At supersonic speed, the pressure change is sudden (in a shock or an expansion fan), and the pressure rise of a shock reaches into infinity.

Yes and no. There must be a gradient between the low pressure at the surface and the atmospheric pressure in the farfield. However, for boundary layer analysis (Blasius solution), one of the key assumptions is that there is no pressure gradient in the wall normal direction.

Because of the low surface pressure, there is a normal pressure gradient.

Yes, in the farfield


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Are cabin temperatures related to destination weather?
I've been in a long-distance flight between northern and southern hemisphere, with temperatures nearing 5°C on the origin, and 25°C on the destination.
During the first flight, the cabin was excessively hot; one possible explanation would be that the sun was shining on my side of the cabin, and the new "no-blinds" system, even when darkened to block most of the light, was still unable to contain the heat.
However, on the return flight (from hot area to cold area), the sun was also shining on my side of the cabin, yet it was much colder (note: I was wearing exactly the same clothes in both flights), as if the cabin temperature had been deliberately set, in both flights, to match the weather at arrival.
I couldn't find any information about this policy. Is it just coincidence? Are companies supposed to follow some set of rules to e.g. minimize temperature shock when arriving?
Edit: The aircraft was a Dreamliner.

Do you remember the airplane's model?

When you come out of a 5°C environment, a 20°C environment feels warm. When you come out of a 25°C environment, the same 20°C environment feels cold. Not saying that this was the case here, but it could play a role.

@sophit : a Dreamliner, I just added it to the question.

No. There are no global rules of this nature.
However, some airlines set their own rules, usually setting the upper limit at 29-32 °C and the lower around 18-20 °C. Some pilots will clearly have preferences for warmer or cooler temperature.
But this is only incidentally related to the destination - you're more likely to be flown to Scandinavia by a Scandinavian pilot, and to Africa by an African pilot on an African airline than vice versa. More likely, not a rule.
Most passengers will spend at least an hour at the airport after disembarking, and airport indoor temperatures vary only slightly around the world.

Yikes! Having a cabin temp of 29-32°C (84-89°F) would be miserable even for a short flight! I'd sleep well, though - that kind of heat and stuffy environment would put me right out...

@FreeMan Not a joke. Most pilots will target 80F or less, but they will fly with a hotter cabin if it doesn't work out.

Ugh... Never taken a thermometer aboard with me, but I'm pretty sure I've been in some hot cabins. Probably never quite that hot, though. Once the engines spin up and the PACS are fired up, temp usually comes right down.


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What punishment will I get from CASA if I fly in a cloud while a student pilot?
I am a student pilot in Australia. Someone said he saw me fly into a cloud at 1700 feet above ground level for five seconds. But I am sure I did not fly in the cloud. I have no instrument rating, nor a pilot license yet. I am grounded and waiting for further investigation.
What punishment will I get from CASA if it rules I flew through a cloud?

Well, if they find that you didn't, I'd bet you get no punishment. Do you mean "what punishment do I face if they find against me?"

yes,I do mean if they find against me.

I have had a fair bit of experience with CASA, including a close friend who worked for them for a number of years. They have a bad reputation these days but I'm not sure it's entirely deserved. I obviously cannot predict exactly what they would do but I hope to give you some advice.
First things first, I would believe your version of events much more than someone on the ground - slant visibility and all that.
The regulations (CAR 172) effectively states that if you fly into cloud the penalty is 50 penalty points - I think each penalty point is currently 110 dollars so the answer to your question is you could be fined $5500. However, CASA uses discretion as to when to enforce this fine - and the Department of Public Prosecutions gets the final say. If it is not a good use of their time, or if it doesn't really serve the public interest, they won't bother with it. A student pilot who accidentally flew into cloud? I would be very very surprised if they followed it up - particularly because as a student you are under the care of an instructor, who shouldn't let you fly solo if there was cloud in the immediate vicinity.
I don't think this would apply to your situation, but a more common course of action for CASA is the "fit and proper person" catch-all. Basically it means CASA must be comfortable that you will be responsible with the powers your licence gives you. CASA uses this power to remove the licences of people who frankly, shouldn't have one. It tends to be reserved for people who break the law either intentionally or through gross negligence. Also for example if you are charged with a non aviation offence, like fraud, CASA might take your licence claiming you are not a fit and proper person to hold one.
Other items in CASA's arsenal include temporary licence suspension, forced re-training or re-sitting of an exam or flight test. There is also a 'demerit points' system if you are a repeat offender.
Some general advice now (remembering that I'm not a lawyer) - don't lie. According to my friend (who should know), CASA is more concerned about your attitude than anything. They want to see people taking responsibility for their mistakes and accepting the consequences. This certainly doesn't assure you immunity but you might find that this reduces a licence suspension from 24 months to 6 months. If you are particularly worried, remember that you don't need to tell CASA anything if you are the person under investigation - like in other legal matters, you have the right to remain silent. Before any action is taken against you you will receive a "show cause" notice, which tells you what they are planning to do and invites you to tell them why they should not do that. If you don't like what they propose I'd advise upon getting a lawyer to respond on your behalf.
But all pilots make mistakes and only 'temporary pilots' pretend otherwise. If you really did fly into that cloud, thoroughly debrief with your instructor and turn it into a learning opportunity. If CASA does come knocking then you can talk about what you have learned and that you are a better pilot for it.
But, in the circumstances you've described, especially as a student pilot, if CASA comes down on you I would be questioning where my taxes are going. What you are going through must be intimidating but don't be fearful - if your goal is to get into the airlines you will quite likely experience this sort of situation again. As long as your intent was never to break the rules or put anyone in danger, you honestly should be fine.

thank you very much,sir!Your advice give me a very clear guidance and make me feel release.Now I would calm down and recall what happened.The weather of that day changed rapidly before and after I took off.The ground was been in my sight when the incident happen.I have reason can convince myself I did not fly in clouds.I will  confidently waiting for the investigation.

Good to hear. It is difficult when the weather is changing rapidly - the key is to make an early decision to either land or divert, and stay well away from the clouds. It's not safe if you can't easily see the horizon. Think about what you could have done differently and talk to your flight school about it. Good luck with the investigation and your future flying.

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Why is the B737 altitude display unneccessarily ambiguous?
I was playing FSX again lately and was flying the B737-400. So I hope it is simulated correctly and this question isn't dead on arrival :-)
It always bugged me, that the altitude display on the MFD is very ambiguous when you are immediately below a "round" value:

On first glance everyone (ok..me) would read the altitude to be 9900 ft. Only if you know what to look for and spot that the numbers carry on downwards you can deduce that you are actually at 10000. The reason is that the second significant digit does not roll over smoothly but ticks over appruptly when the next round value is surpassed.
Granted, 100 ft may not be a huge difference, but it seems very unneccessary to have it like that. If the first two significant digits behaved more smoothly without this round-down like behavior I would recon that it would be way less ambiguous.
Why is the altitude display designed that way?
Edit: Here is what it looks like in motion:

I think it is an artifact of the simulator after all; the real display isn't like that.
The way that you describe the behavior of the altimeter tape in the simulator is that

the second significant digit does not roll over smoothly but ticks over appruptly when the next round value is surpassed.

However, in the YouTube video "Boeing 737 cockpit instrument approach landing" (uploaded by aviafilmsproduction on Jan 6, 2015), we can see that the hundreds digit does "roll over smoothly" rather than "ticking over abruptly," so there isn't really any ambiguity.
The video shows an altimeter tape which initially reads 3840 and gradually decreases. The two rightmost digits scroll constantly. After the number reaches 3800, the three rightmost digits all move up together; the "800" part moves out of view and is replaced with "780". So, the altimeter never falsely appears to read 3700 or 3870. Likewise, after the number reaches 3000, all four digits move up at the same time, being replaced with the number 2980.
I'm not sure what the altimeter tape in your screenshot is trying to say; the analog portion (the "ruler" with tick marks) seems to be reading about 9960, while the digital portion (the "odometer") looks like it's reading 9900, and you're saying that it's actually reading 10000. In any case, judging by the video I linked to, in the real Boeing 737, if you're much closer to 10000 feet than to 9980 feet, then the altimeter will appear to read 10000, not 9900.

Thanks for the description and video link. I found one climbing as well and there it is the same deal, behaving like you would expect a number "ticker" to work. I'll cross check with the sim later, maybe it was indeed badly designed (or updated in the meantime, because I think its based on ~2005 vintage :-)).

Because thats how old school "steam" altimeters work/look and glass cockpits were designed to work similarly such to reduce unfamiliarity when transitioning. Prior to the screen age a drum altimeter would have read out and increased in much the same way the glass cockpit does now.

(source)
You will also notice the 10's and 1's place's are joined and rounded off by 20's. This has to do with the common arrangement of tick marks on any old altimeter as well as the fact that in a fast climb the one's digit would be unreadable.
On any note, its not ambiguous to a pilot, its actually quite accurate if you know what you are looking at.

Too accurate in my opinion.  I favor a round dial altimeter specifically because of this.  Anything less that spot on gets rounded down, and at first glance you may think you are a thousand feet off.

So with the altimeter pictured in your answer, does the hundreds place “tick over abruptly” when you go from, say, 9,999 feet to 10,000 feet? If so, is there any way for the pilot to distinguish between 9,900 and 9,999 at a glance? If it doesn’t “tick over abruptly” like the glass altimeter in the simulator does, then I don’t think this answers the question.

@TannerSwett here is a video of it in operation, it does not tick over that hard https://www.youtube.com/watch?v=kFxfy5wQsq0

@Dave thanks, yes with this style seen in the video as also mentioned by Tanner Swett it is much better and behaves more like you would with such a number ticker. I'll add a video later when I get home to illustrate how it looks in FSX. Any chance something like this was changed or updated in the real cockpit in the last 15 years? :-)

Please see edit to OP for a video.


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Why was the deep-stalled prototype Velocity unable to come out of the stall, even with a 20-30deg nose-down attitude?
Test pilot Carl Pascarell got himself into an interesting situation while testing the Velocity prototype. With an aft-CG, he got himself into such a deep stall that flight was unrecoverable. Amazingly, when he prepared to bail out he noticed that his decent rate with the plane was the same as it was with a parachute, so he decided to ride it out.
Along the way down, he tried several strategies to coax the plane into flying again. The one I find the most interesting is when he achieved a nose-down attitude, but was still unable to recover from the stall:

Oscillating the aircraft with coordinated rudder and aileron, he was able to achieve a 30- to 45-degree bank and a 20- to 30-degree nose-low attitude. Progress? The airspeed indicator showed 20 to 30 knots, and the descent rate increased to 2,500 fpm; but several coordinated 360-degree turns later it was clear that the new method was useless.

What was going on aerodynamically? What was going on to allow for coordinated turns but not for pitch control?
Source article: https://www.aopa.org/news-and-media/all-news/1996/june/pilot/pilots-(6)
(Another explanation worth considering: the article is a little loose on details.)

@Pilothead I have no idea how I neglected to include the article link, esp. since I copy-pasta'ed from it for the quote. Thanks!

So a pilot was in a plane with no power, falling, and could have escaped, and chose not to?!

@Someone. Yes. He determined that he was safer in the plane than outside of it. Events proved him right.

@Someone, he had a parachute, but it would be an emergency parachute that is relatively small so the landing would still be pretty rough.

The deep stall at aft CG in a Velocity was discovered by the first customer, Neil Hunter, who was not seriously injured in his episode. The stall was duplicated by Pascarell as you mention in the company aircraft at the request of the designer, Danny Maher, showing that there was indeed a design flaw.

To discover the cause the aircraft was mounted at its aerodynamic center on a trailer with a 210lb internal weight which could be shifted forward and aft through the entire cabin. The mount allowed the aircraft to pitch up to near vertical. As the descent speed in deep stall was only 15-20mph the trailer did not need to be pulled very fast.

With the aircraft tufted and cameras mounted, a series of tests showed that the main wing stalled at 18deg, the canard stalled at 20deg and the strakes (which were ahead of an aft CG) stalled at 26deg, leading to pitch up. In a canard the main wing needs to stall last to avoid unrecoverable deep stall and in the original configuration it was stalling first. This contains a description of the tests.

The solution for kits already being built was the installation of a main wing cuff similar to this test article. The wing design was changed for future kits which included an extended trailing edge and modified camber on the aft strake such that no deep stall could be entered, thus not requiring the use of the cuff.
Update: There is at least one discrepancy in the article which states that the "rudder and elevator were useless" when in the stall and also states that the pilot oscillated the aircraft with "coordinated rudder and ailerons". It seems likely that since the aircraft was longitudinally and directionally highly stable in the stall, the turns were initiated by banking with ailerons and airframe stability coordinated the turns. The banked turn increased g loading resulting in a higher rate of descent in an accelerated stall.

Alas, 2500 fpm is also around 30 knots, so the descent angle was around 45 degrees.  The pilot may have been close to breaking the stall, but not quite.
The "coordinated turning" was probably a combination of yawing from drag difference of the stalled wings, the lift differential from one being more stalled than the other, and rudder inputs.
Attempting spin manuvers with aft CG is dangerous, but we have to applaud the pilot for staying with it because the rate of descent was similar to bailing out with a parachute.

I often wonder about the judgment of staying with the airplane.  Granted, survival chutes may be smaller but as someone who’s been a pilot, paratrooper, and skydiver, no one’s descending under a canopy at around 30 knots.  Typical descent rates are in the 17-19 mph or 14-16 Kt range.   30 kts is the equivalent to jumping off a 4-story building and landing on your feet, and would rarely be survivable.  I’m assuming that he took the energy absorption of the aircraft into account, but a 30 Kt impact is still a dangerous situation.

The 2500 ft/min decent was while he was trying to maneuver the airplane out of the stall. His decent rate while wings level was considerably less. He was also over the ocean.


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What are these small engine inlets on the Super Hornet?
Does anyone know what these two small variable inlets on top of the engines are used for on the Super Hornet?

Source: navy.mil; cropped

That is one tired looking aircraft.

Navy airplanes at sea just don't have the luxury of periodic baths.

@CarloFelicione  It is far easier for a Navy plane to take a bath than for most land-based aircraft...

Another luxury they don't have is periodic paint.  Aircraft paint and marine paint both have hexamethylene diisocyanate in the resin. Marine paint is formulated for brush or spray. For brush, PPE is wear gloves and cordon anywhere within 6' of the wet paint.  For spray, PPE is a moon suit and cordon anywhere overspray could drift to, in short, you will not spray while underway. Hence, brushing.  Aircraft paint can't do that.

These are the auxiliary air inlets for the ECS (Environmental Control System):

(image source)
They provide air to the primary heat exchanger (A18), which is then exhausted via the ram air exhaust (A20, the tubes visible behind the inlets in your picture).


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What, if any, equipment on a commercial airliner is (allowed to be) inoperative most of the time?
Since airliners are bound by their minimum equipment list, I was wondering, which parts/systems that are not on the minimum equipment list are often inoperative on normal commercial flights.

Do you mean dispatching with systems inoperative or systems that crap out during the flight?  If it's inoperative on the ground, and it's not covered by an MEL, you're stuck.

Yes I mean dispatching with systems inoperative. Systems that are not required for the flight by the minimum equipment list.

this question is really broad. each aircraft types has its own equipments. you should restrict to one or two specific aircraft types (e.g. B737, A320, E190). Each airline may have its own restrictions (more restrictive than the manufacturer ones). Thus you may restrict to few airlines.

The Blue Angels show team formerly used the Lockheed C-130T Hercules, nicknamed "Fat Albert", for Jet Assisted Take Off (JATO demonstrations). These ended in 2009 due to dwindling supplies of rockets. Hence, since then the JATO system is not operational.  I do not know if this team is "commercial" enough.

If a system goes south while sitting at the gate or the ramp, that brings on a cockpit indication, the crew will break out the MEL/CDL using whatever protocol or procedure they follow and if it's not covered, they are grounded until the system is made serviceable again and will take a significant dispatch delay, or worse, a cancellation.
The OEM will try to get as many items covered under the MEL as possible and will continuously try to expand it, because it has a big effect on overall dispatch reliability.  An unreliable system system or subsystem that has a lot of failures will just be maintenance cost issue (and possibly minor delays) if it has MEL coverage, but if it doesn't, it becomes a cost plus dispatch delay/cancellation problem, much more expensive.

Are you sure it's not backwards: a non-MEL system is just mx, and a MEL system is mx+delay?

No a non-MEL item causes a delay or cancellation because it has to be repaired and made serviceable before you can fly.  If it has an MEL, you can dispatch with it inoperative after doing a deactivation procedure or maybe just a simple crew procedure.  In some cases you might take a minor delay if a tech has to go in and blank something off.


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What are these features on the V-22 ospreys rotor?
On the outside of the V-22s rotor fairings there seems to be some kind of hinged weights directly opposite of each of the three rotor blades. Does anybody know what their purpose is?

They appear to move from side to side in that curved slot, either passively or by actuation, so they are likely used to control vibration/harmonics in some way by offsetting the center of mass of the hub. That kind of thing looks like a bandaid, developed to fix a problem to avoid a bigger redesign.

And also with that aerodynamic shape I expect that they rotate to align with the local airflow.

If I were to take an educated guess I might say they are counterweights to provide a countervailing force that drives the blades to a safe pitch angle in case of actuator failure.


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How does Boeing Deliver single aisle jets to South east Asia?
I am not sure if they can fly on full tank gas to their destination (say India or Thailand), but how does Boeing deliver single aisle jets to these destinations. I read somewhere about the process of delivery, but I am more interested to know what kind of skip hop flights do they take for delivery? Any way we can track new outgoing aircraft?

Also related

Magic. More specifically, science.
Even regional aircraft are generally designed with 3,500+ nmi range with some load, and more without. It's more than enough to travel to anywhere in the world, given some refueling stops.
In fact, even WWII combat aircraft, which had a fraction of modern airliner range (though it took a big dip once we went from props to jets), were able to travel to both Europe and Japan for duty.

They ferry them out there, same as any other aircraft.  The plane can be fitted with ferry tanks inside the lower baggage area to increase the range as needed for the flight or multiple stops may be made.


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What are the not-winglet wingtips on the CL-415?
JohnK left a tantalizing "the weird turned up wing tips on the draggy slug CL-415 water bomber aren't winglets at all" comment in https://aviation.stackexchange.com/a/52140.
So what are they, then?

https://en.wikipedia.org/wiki/Canadair_CL-415

I know an aerodynamicist who was involved in the program who explained them to me years ago. They are not winglets or end plates. They are what you might call "dihedral tips".
They were added during CL415 development because the replacement of the CL215's round profile radial engine nacelles with the flat turboprop nacelles, during the redesign to the CL415, killed off too much of the aerodynamic dihedral effect created by the T wing-to-fuselage junction.
Recall that dihedral effect is a counter-rolling response to side slip when an aircraft banks, to provide stability in the roll axis. The 215/415 has zero geometric dihedral and depends solely on the wing/fuselage T junction for an aerodynamic dihedral effect to provide the desired roll stability (span wise flow is inhibited below the wing by the fuselage during side slip, but not above it, increasing lift on the low wing).
Thus roll stability was found to be degraded because the "high wing" configuration was effectively turned into a more of a "mid wing" by those big flat fin-like nacelles sticking up, inhibiting span wise flow (the same as a fuselage sticking up in a mid wing configuration) much more than the old round nacelles did. In other words, to the extent that a nacelle projecting above the wing profile acts as a flow fence, the flat TP nacelle is a much more efficient flow fence than the radial engine nacelle was.
The turned up tips generate the required counter-rolling response during side slip, sufficient to compensate for the effect of the flat nacelles, and restore the original roll stability. They are angled in a way that gets sufficient rolling moment with side slip (the axis of the lift force generated will pass above the center of mass) without creating much of a vertical lift component that would increase bending loads on the wing root.
In effect, they are a band aid solution to a problem introduced by the engine change, one of two unforseen surprises. Another problem was that the flat nacelles shifted the vertical neutral point (aerodynamic center) forward, reducing yaw stability and requiring the addition of finlets to the horizontal tail. This is similar to the effect of adding floats to landplanes, which is why you often see ventral fins, dorsal fins, or finlets added to floatplanes when floats are installed.

This maybe should be another question, but why does moving the aerodynamic center forward reduce yaw stability?

If you think of the entire aircraft as a weathervane (pivoting on its center of mass instead of a spike), you need the aerodynamic center of the vane to be behind the pivot so that the weathervane points into wind. You need more surface area behind than ahead of the pivot. On an airplane, adding surface area ahead of Cof G (the pivot), weakens the weathervaning tendency, the yaw stability. Look at the 415's nacelles & notice most of the side area is forward of the wing. When landplanes are put on floats, the exact same thing happens, thus the little finlets on floatplanes as with the 415.

It might be clearer to say that the dihedral tips were added when the aircraft design was retrofitted to have turboprop instead of radial engines. Otherwise, to a casual reader, it seems that they might have made the change during the initial design or something.

@le3th4x0rbot  Made a number of edits. Thanks.

In Germany those were once called "Lippisch-Ohren" ("Lippisch ears", after Alexander Lippisch, who first used them on his tailless designs).

Lippisch Storch IV in flight (picture source)
While the wingtip devices on the Storch and Delta ranges of designs helped in yaw control, later designs used them to correct lateral flight characterictics, like on the Heinkel 162.

Heinkel 162A with turned-down wingtips to correct for too much dihedral (picture source).

They are "end plates".

An end plate is a thin flat plate mounted at or near the tip of the wing, perpendicular to the wing surface and parallel to the airflow. It acts as a fence that opposes the spanwise flow near the tip of the wing.

not "winglets"

A winglet is a wing-like device that extends vertically or nearly vertically up from the tip of the wing. The winglet operates in the cross-flow generated by the tip vortex.
Unlike an end plate, which is flat, a winglet has an airfoil cross section and may also incorporate twist to optimize its aerodynamic effectiveness.

Reference: https://www.kitplanes.com/design-process-end-plates-and-winglets/


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Why did Concorde have a 8000 ft airport elevation limit?
According to the Concorde Flying Manual Volume II(a) - 1 Operating Limitations - page 01.01.02 the take-off and landing airfield altitude is minimum -1000 ft and maximum 8000 ft. Why is Concorde limited to a maximum airfield altitude of 8000 ft, excluding Concorde from airfields like El Alto International at 13,323 ft?

My initial thoughts were either maximum braking action limitations for rejected take-off or maximum tire speeds, but unfortunately the manuals linked above do not mention max tire speed or brake energy limits.
Update: As @gwally pointed out, Concorde did fly to Bogotá, Colombia with an airfield elevation of 8363 ft two times, in 1974 and 1975. So it seems the 8000 ft maximum airfield elevation seem to be a certification limit or operational limit, and not a performance limit of Concorde.

There was no need to serve high altitude airports. The ideal Concorde routes were between harbour cities with only ocean in between. Why engineer something that will not be needed?

Concorde had extremely bad low speed performance (high drag and low lift) as a consequence of it being optimized for supercuise. To the point they needed the extra thrust from the afterburners even at low altitude runways. It may be that there just wasn't enough thrust and/or lift above 8000ft.

@PeterKämpf I would probably agree if you said why certify something that will not be needed, but that is exactly my question, is there a technical limitation why Concorde can't operate form high altitude airfields or did they simply not bother to certify it.

Is that limit MSL or density altitude?

@jamesqf Updated the question with the page from the manual. DA would make more sense performance wise, but it is altitude, above MSL.

@user1937198 Those were my thoughts, but why an absolute limit of 8000ft? If you can make a reasonably normal takeoff at 7316ft (Mexico City) surely you can make a reduced weight takeoff on a cold day at 8100ft, if your runway is long enough?

@DJClayworth That sounds like something that is more likely to come down to certification. But this is pure speculation.

Current day limitations on some airplanes: B744 - max field elevation 9500ft; B787-8 -14000ft PA, use high alt procs above 8000; B777-300ER - Max T/o and Landing - 8400PA

Your question about whether the plane could use higher airports is an interesting one but your demand to know if the limitation is “technical” is IMO not reasonable.  You mean: if there was a need to test and certify the plane for higher altitudes, would changes have to be made to the plane or would it be mainly a bureaucratic effort?   There is only one way to find out: Go back to the plane’s designers, ask them to extend the scope of their work to your new requirements.    Only then would we know if the initial design could extend to new conditions or the current limitation is "technical".

@jay613 I get your point - but I thought it might be the case that someone would have access to additional manuals/documentation in which things like max tire speed, max breaking action or other limits may be mentioned that would explain why Concorde was limited to 8000 ft. But it could also be the case that the question can only be answered by a designer.

I'm actually impressed that it is that high.

Edit: Concorde can take off and land above 8,000 ft
From October 20-28, 1974, Concorde 02 (F-WTSA) made a tour of the American Pacific coast, visiting London (83 ft), Gander (495 ft), Mexico City (7,316 ft), San Francisco (13 ft), Anchorage (151 ft), Los Angeles (125 ft), Lima (112 ft), Bogotá (8,710 ft), Caracas (236 ft), Las Palmas (78 ft) and Paris (392 ft).

http://www.concordesst.com/history/70s.html

El Dorado International Airport - BOG (Bogotá) has an elevation of 8,710 ft (2,648 m), which puts in 710 feet above the limit of the 8,000 ft maximum altitude. Both runways are 12,467 ft (3,800 m), so capable of handling a take-off.
In addition, Air France flew Concorde twice weekly to Mexico City's Benito Juárez International Airport - MEX (Elevation AMSL 7,316 ft / 2,230 m) via Washington, DC, or New York City, from September 1978 to November 1982.http://www.concordesst.com/history/70s.html
This shows that Concorde was able to schedule regular service to an airport 684 ft lower than the 8,000 ft maximum altitude and visit an airport above 8,000 ft.
I am not sure the 8,000 ft is a hard maximum elevation. It could be for a fully loaded plane. I have not seen any chart to show maximum take-off weight at any altitude.

I would argue quite valid - if it is certified up to 8000 ft. elevation, I see no reason why it would not be used up to that threshold. I mean it is the same with other limits as well, TOM probably being the one that is most often close or to equal to MTOM. Nice postcard BTW!

@wowpatrick I second that. 8000ft take-off ceiling means among others that 7316ft is allowed.

It's quite likely that the engineers chose to design for an 8000ft limit because they knew they wanted the plane to fly to Mexico City. In any case, this doesn't answer the question which is "why"? (Presumably "why was it not higher"?)

@DJClayworth Concorde did land and take off at least once at 8,710 ft in Bogotá. So apparently it could go above 8, but maybe not for regular service.

Why is this downvoted to -3? Is anyone downvoting also explaining why in a comment?

Agree with @zymhan - this shows good background research


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Is the differential between the forward and aft CG limits indicative of the overall stability of an airplane?
Studying up on the Cessna 162 Skycatcher POH to take my checkride in soon and I noticed the differential between the maximum and minimum CG's is a mere 2.5 inches from one to another.
I got curious and looked up the CG limits for the two other planes I train in, the CSA/CZ SportCruiser and the Cessna 172, and saw that the differences between their forward/aft CG limits are 6" and 12", respectively.
In terms of aerodynamic stability, I would indeed rank the Skycatcher (2.5" CGfwd/CGaft differential) as the least stable and the Skyhawk (12") as the most stable. Is there any connection between forward/aft maximum CG differentials and the amount of aerodynamic stability in an aircraft?
Edit:
Still reviewing the responses, having been sent to the encyclopedia several times to study up on new terminology, but I just want to emphasize that the  SportCruiser (6" diff) is dramatically more stable in the air than a Skycatcher (2" diff). Both of these aircraft have the same max gross takeoff weights, 30 foot wingspans and 23 foot lengths. So perhaps the Cessna 172 could be ignored for the purposes of addressing the question.

https://en.wikipedia.org/wiki/CZAW_SportCruiser
https://en.wikipedia.org/wiki/Cessna_162_Skycatcher
https://en.wikipedia.org/wiki/Cessna_172

Very interesting question. Might be worth normalizing the intra-CG limit differential to something else too, like the plane’s overall length or the chord length. (You’d expect a smaller plane to have a smaller differential than a bigger plane for the same stability characteristics.)

@Peter, true. Engineers usually express the CG range (as well as the static stability margin, i.e. the distance from CG to the aerodynamic centre, and several other characteristics) in terms of Mean Aerodynamic Chord. So the range may be specified as, say, 15..25% MAC. But MAC is a theoretical value, so a fixed station and physical units are often more convenient for pilots and service personnel.

Normally, the aft limit is governed by static stability, while the forward limit is governed by the elevator control capacity (but sometimes, dynamic stability: excessive static stability may cause oscillations).
So, a narrow CG range would rather suggest that the elevator and/or trim capacity is not sufficient to cope with the more forward CG.
However, in practice there may be other reasons for restricting the range. For example, it may simply be impossible to load the aircraft (without exceeding the station load limits) in such a way as to put CG out of the defined range. I think C152 is close to that. Or, say, the stall or spin characteristics are unsatisfactory, so the aft limit may be restricted further than what normal stability dictates.
Needless to say, artificial stability augmentation (including FBW) may broaden the CG range, primarily by affording a more relaxed aft limit.

Expanding on the reasons is the expected utility of the aircraft.  The 162 is a small trainer with 2 side-by-side seats and limited baggage space. It's just not possible to move the CG very far. OTOH a Cessna 206 or 210 with three rows of seats needs to be able to accommodate a much larger variation in loading options -- from 2 fat guys in the front to a family of six with baggage.

You may enhance your answer by adding drawing and references to illustrate and support your answer; and to provide further reading.

Wouldn't one expect the aircraft's static stability to govern the location of the middle of the allowable CG range, with both the forward and aft limits being defined by the aircraft's maximum pitch control authority?

@Sean, no. The middle is not really any sort of equilibrium or the optimum. The farther aft the CG is, the less statically stable the aircraft is. To control a statically unstable aircraft, one needs extremely fast responsive controls (normally driven by computers), but not necessarily 'strong' ones. Sure, at some extreme you'll hit the limit again, but this will not be due to insufficient moment produced; rather, because hitting the travel limit denies you the opportunity to make further dynamic corrections, which are vital to compensate instability. This applies only to really unstable a/c.

Aerodynamic static stability is controlled by the distance between the center of gravity and the neutral point of the aircraft. A limited c.g. range has nothing to do with stability per se. Every aircraft gets more stable, and more heavy on the controls, when the center of gravity is moved forward.
Two-seaters with little payload, as LSA tend to be, need less c.g. variation than four-seaters which should be flyable with the rear seats both occupied and unoccupied without adding ballast. I would guess that Cessna restricted c.g. travel even more when they cured the Skycatcher of its flat spin tendencies.
For the rest of the effects please read Zeus' answer. I see no need to replicate its content here.

authors: ΠΑΡΙΣ ΚΑΛΟΔΗΜΙΔΗΣ

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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What are ICAO English language requirements?
As a supplement to this SE question; "What are the requirements to become a language proficiency examiner?" (something I never heard of...) What are  ICAO English language requirements?

Related, perhaps a dupe?

ICAO defined a framework of language proficiency levels for aviation. It ranges from level 1 ("Pre-elementary") to level 6 ("Expert" / native speaker). Level 4, "operational", is the minimum required for flight crews. Many airlines require at least level 5 from their pilots.
Native speakers can get level 6 with a simple proof of that they're a native speaker (I heard recently that e.g. for a German license the authorities see it as sufficient if the person visited an English speaking school). Non-native speakers do assessments to certify their language proficiency. An assessment for level 4 has to be repeated every 3 years, level 5 lasts 6 years and level 6 is life-long.
For languages other than English, there are assessments / language proficiency certifications that are regulated by country-specific authorities and it's practice in at least some countries that native speakers can get their native language put into the license as level 6.
There are detailed requirements for each level (e.g. pronunciation, vocabulary etc.), they are usually presented in a big table:


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Why can some runways only be used from one end?
Is there any reason for why some runways can only be landed and taken off from one end and not the other, even though there aren't any obstructions (mountains, etc.) and apparently can be used from both ends?

Sometimes it’s simply regulations and agreements. Do you have any specific example in mind?

Related/example: Why can't runway 18 at Frankfurt Airport accept takeoffs or landings in the opposite direction?

Noise abatement procedures is probably the most likely reason.

Even if there are no physical obstacles visible - the airspace structure can be somewhat more difficult and one runway direction might run into other reserved airspace. Or just go over noise-sensitive neighborhoods...

Besides airspace reserved for e.g. military purposes, it might also be take-off/landing paths to other runways.


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Identify canard, low-wing, single pusher-prop plane over Upstate NY
Yesterday, August 11, at around 3:30 pm, I saw an unusual-looking plane flying over Ithaca, NY. It seemed fairly small -- approximately business jet sized. Unfortunately, I didn't have time to get a picture, but I remember several distinctive aspects of its appearance:

Canard and seemingly no conventional tailplane
Single pusher propellor
Low, swept wing with winglets. Pretty sure it was tapered.

I only saw the plane from below, so I don't know anything about design aspects on the top side of the plane. I checked on FlightAware and FlightRadar24, and didn't see any obviously-matching flights, but I may have missed something. Based on some googling, what I saw seems pretty close in appearance to the AASI Jetcruzer (picture below), but apparently only five of these were ever registered, all in California. According to that same page, only one remains registered, most recently in Washington. The most recent flight recorded with its tail number (N200JC) by FlightAware is from 2014.

AASI Jetcruzer
Additionally, the wing profile doesn't look quite right to me. Another somewhat similar-looking plane that has a more correct-looking wing is the Beechcraft Starship (picture below). However, I'm quite sure that what I saw only had a single propellor. According to the same website, only one specimen of this aircraft remains registered, and similarly its last flight recorded by FlightAware was in 2011.

Beechcraft Starship
Are there any more likely possibilities for the aircraft I saw than one of these rare and seemingly seldom-flown planes?

Are you certain it was biz-jet sized?  Because the Long EZ (and possibly others...) fits the description.

Not 100% sure, but I am pretty sure it didn't have the prominent fixed landing gear pods of the Long-EZ.

What did it sound like?  High pitched hum like a turbo prop, or a brakkabrakkabrakka piston engine sound?  Based on relative numbers, it's almost certainly a Long Eze or one of its derivatives like the Cozy.

More of a piston engine sound, I think. I still think the plane was low-winged, but I may have overwritten my mental image with the image of the two planes in my post.

There ya go.  Probably an 80% probability it's a Long EZ.

There are a number of near-copies of the Long EZ, with nearly identical wing and canard shape; they differ in number of seats, performance, range, and, yes, several of them have retractable gear.  I think there's at least one that's pressurized.
Without a high quality photo (possibly even with one, if shot from the ground), it may be impossible to determine what you actually saw -- but a single pusher propeller, low mounted cranked/swept wing with tip fins, and swept canard originated with the Long EZ (before that, there was the Vari-EZ with unswept canard, and the Vari-Viggen with a different wing sweep profile).

The Adam A500 would be the right size. Wikipedia has more info.  It is a twin but it has a pusher prop and a canard. There were only five made and two flying:  N510AX and N510AX have recent flights in Pennsylvania, so it’s possible you saw them in New York.

Interesting answer, especially with the dual tractor and pusher props. Pretty sure it didn't have that looped tail though.

Unless it's invisible against the fuselage due to the angle, that aircraft does not have a canard.  It's a conventional layout with twin boom to clear the pusher propeller (like a low-wing Skymaster).

@ZeissIkon You are right. My thought these had a canard, but I guess not.


text:
Credible Sport Project: Is it possible to revive the idea with modern avionics?
Synopsis: On a secret mission to rescue 52 hostages in Iran, Operation Credible Sport was created. The project consisted of a modified Lockheed C-130 Hercules and developed so that it would be able to land on a runway as short as a football field. In order to shorten the landing distance, the engineers retrofit the planes with rockets.
These rockets slow the planes as it lands and provide extra propulsion upon take-off.
During training in October 1980, just days before the surgical operation, "Operation Credible Sport" derailed.As the plane came in for landing, the pilot mistakenly fired the rocket before the wheels touch-down. The plane loses lift and slams in the tarmac.
For illustration purposes, here is a short video summarizing the event: Credible Sport Test YMC 130 H
Now, technology has come a long way since the 80's; avionics have greatly improved and the aviation industry even came up with the fastest transistor ever-created in 2009 thanks to Northrop Grumman.
That being said, would it be possible to revive this project and allow an automatic firing of the rockets by a computer system rather than by a manual control of the pilots(given that it was human factor that doomed it to failure in the beginning)?

It wasn't a lack of technology. The technology to automatically fire the rockets is not actually very complicated: a radar altimeter, airspeed data and maybe input from the landing gear load sensors hooked up to a simple computer. All of that existed back then, and the rocket system was in fact computerized:

The Lockheed test crew then assessed that the computer used to command
  the firing of the rockets during the landing sequence needed further
  calibration, and elected to manually input commands.

So the plan was to use computer control, but it needed more development than they had time for - as were in a very big hurry they decided to do it by hand.
If they'd had more time to adjust things they no doubt would have succeeded with the technology of the time. The reason that the project was canceled was not a lack of technology but that the hostages were released.
In reality the plan to use rockets to slow down the airplane so quickly was extremely risky, and if it went wrong the US military would have had their best special forces units stuck in the middle of Tehran! I personally don't think this would have gone ahead even if the tests had been successful. The fact that they continued to develop the concept into the MC-130 Combat Talon II without the rockets indicates to me that the military thought the braking rockets part of it wasn't worth it.
So no, modern avionics really would have nothing to do with it.

I was not aware that it was indeed time and not technology that made the decision to control the plane manually.

Sure, you could, but for that kind of mission these days there are far better choices. For instance, a Bell-Boeing V-22 Osprey could be used for such a mission, is rack ready now, far easier to control during takeoff and landing, and makes use of modern avionics and mission systems.

The V-22 actually wouldn't work for that mission. It has an effective combat radius of about 680km, and the route they would have to have taken to avoid air defenses would have been greater than that. In any case it wasn't a lack of avionics that caused the concept to fail.

It was indeed the Iran hostage crisis which largely spurred the v-22 development. Up until then, tiltrotors and tiltwings had been little more than a cute idea but not deemed really practical. But after the failure of the hostage rescue,  the US DoD decided that they really did need a high-speed VTOL.

@GdD Not necessarily.  If a friendly nation like say Turkey allowed us to conduct mid air refueling over their territory, that mission is easily possible.  And, if you’re really committed to such a mission, the use of additional SEAD/DEAD packages could be utilized to clear a path.

Even being able to refuel over Turkey wouldn't have been sufficient @CarloFelicione. A rescue mission would require surprise, they would have to do low-level penetration evading air defenses, which would eat up fuel.

@GdD: this seems like a difficulty that could be dealt with. You could use several aircraft for the mission, some would have the sole purpose of re-fueling the main VTOL.

Mid-air refueling over a hostile airspace wouldn't work out very well @QuoraFeans.

Actually both routes are well within the capabilities of a V-22.  Either a route from the Persian Gulf or Turkey is about 350 nm one way, which is well within the range of the aircraft.  Add in aerial refueling prior to entering hostile airspace and a tanker either leaving and you’re set.  An additional engineering solution may be to design expendable, quick removal ferry tanks which can be removed and abandoned at the landing site during the pickup.  That’s a far easier solution than trying to revive the YMC-130H program.


text:
Can a US state declare an airplane unairworthy?
(This arguably is a question for SE.Law, but because it's so aviation-specific I figured I would ask it here first)
A partner got this in a routine excise tax email from the Massachusetts Department of Revenue (MA-DOR):

Our records indicate that your Aircraft Registration in the Commonwealth of Massachusetts is set to expire on December 31, 2023.
If your Aircraft Registration has expired, as the aircraft owner, you cannot legally operate your aircraft until you receive your 2024 new registration certificate.

This got me a little curious. I could certainly see a state law which forbids locally registered aircraft from landing/taking off at state-owned airports, but I don't understand how one state can revoke airworthiness from the national airspace system. (I only have that excerpt to go off of, so don't know if a specific US or MA law was referenced. Thanks to @Chris, we have the relevant MA law: https://www.mass.gov/files/documents/2017/10/30/702cmr3.pdf)
Does a US state have US-wide airworthiness authority over airplanes registered within that state?

Update
I think this question is somewhat confusing because of a widespread mistaken understanding of what "airworthy" means. As MichaelHall shows in his answer, it's definition is "the aircraft conforms to its type design and is in a condition for safe operation." Unfortunately many of us, myself included, were taught that full paperwork compliance was also required for airworthiness. This led to me using the wrong word in the question.
I'm going to keep the original question as asked, because the answers are not wrong vis-a-vis the original wording. Fixing it would do a disservice to the existing answers, and if I need further clarification about state's ability to regulate aviation outside their borders I will ask at SE.Law.

No, and Massachusetts law doesn't claim to. Massachusetts only forbids you from flying in Massachusetts if you are supposed to register in Massachusetts and fail to. From 702 CMR 3.02(6):

No person shall operate an aircraft or permit any other person to operate such aircraft within the commonwealth unless the aircraft is permitted to operate within the commonwealth pursuant to M.G.L. c. 90, § 48, 14 C.F.R. Subchapter C and 702 CMR 3.02(1) through (4).

Note that "the commonwealth" refers to Massachusetts in the text above.

Thanks! I was not going to find the CMR on my own. Not to contradict, but a lay reading of that law would seem to forbid a tax delinquent from flying in or over MA, i.e. the airplane is out of compliance with the law and is thus no longer airworthy from a regulatory perspective (which is legally just as strong as from an MX perspective). Is there a nuance in how "operate" should be understood in the above context? In the FAR, operate clearly includes "fly", and so with that same understanding of "operate" that CMR would seem to restrict said planes from being airborne over MA.

@KennSebesta I agree with your reading that the law forbids flying in or over Massachusetts. But this doesn't make the aircraft unairworthy from a Federal perspective- if you operate the aircraft in Massachusetts you are in violation of state law but not in violation of Federal law.

that's a fair point about the Federal perspective, but is that the only perspective for overall airworthiness? Or is there a "forbidden to fly but not unairworthy" clause in the FAR which would permit states to declare an airplane unfit to fly? Because from https://aviation.stackexchange.com/a/77475/20394, it seems that the FAA is very clear that the states have 0 authority "to regulate any type of aircraft operations", which would be in contradiction to the CMR which regulates aircraft operations.

@KennSebesta This law, if it were applied to overflights of Massachusetts that do not land anywhere in the commonwealth is probably unconstitutional. But states and local authorities can regulate what happens on land. Since 702 CMR 3.02 only applies to aircraft based in Massachusetts it's hard to imagine a situation where it would apply to you if you never land in the commonwealth, so it may be a moot point.

It would certainly be unconstitutional to try to force non-based aircraft that fly over Massachusetts to register there.

Excellent point. Thanks! It sounds like the law can constitutionally apply to ground operations, and a perhaps overzealous MA-DOR representative unwittingly over-projected MA's power over the NAS.

@KennSebesta Perhaps. It's not clear that it's a real overreach since it only applies to based aircraft that spend a lot of time on land in Massachusetts. A much more blatant overreach is Massachusetts' law about Altitude of aircraft flights!

@KennSebesta, "Unfit to fly" and "airworthy" (or non-airworthy) are terms not mentioned in either the letter your friend received, or the law you linked to.  Registration with the state is simply an administrative requirement they have enacted to generate revenue.  You are reading more into this than is there.

@MichaelHall maybe you meant that as a comment in my post and not this answer? That aside, I'm sure you're aware that airworthy is not a "fit to fly" but a "legal to fly" determination. The upshot is I don't see how, with a plain reading, anyone is meant to understand "you cannot legally operate your aircraft" aside from a blanket, nationwide prohibition, i.e. an effective AWC revocation. What I think Chris has demonstrated is that the boilerplate in the form email is not consistent with the MA law, and it is not, in fact, a nationwide prohibition.

No, i meant to comment here, specifically because of your ongoing questioning of Chris' complete and excellent answer.  The trigger was asking whether there might be a "forbidden to fly but not unairworthy' clause in the FAR...".  Space here doesn't allow much more than this, perhaps i will expand my thoughts into an answer to further my point.

"I don't see how, with a plain reading, anyone is meant to understand "you cannot legally operate your aircraft" aside from a blanket, nationwide prohibition." NO!  Nobody is meant to understand that any law applies outside of the jurisdiction of the legal entity that drafted the law. Putting the definition of "airworthy" aside, jurisdiction is a fundamental principal of law, and you are reading an "overreach" into this that just isn't there. Nothing in the Massachusetts law hints at applicability to owners registered outside the state.

@MichaelHall you're picking an odd fight here. When a representative of the gov't tells you something is illegal, then you're meant to understand it is illegal. Full stop, no ifs ands or buts. Now, you and I both know that representative's email is wrong, but that doesn't change how the general populace will understand it.

I'm not picking a fight, i am simply trying to get you to realize the truth of what has been presented to you. That representative's email wasn't "wrong,", it just just has nothing to do with airworthiness, and applies to Massachusetts only. I believe the general populace understands that. Please reference my answer and let me know if anything is unclear.

@Kenn I think a lot of the grief you're getting is because you keep using the term "airworthy" when it doesn't have anything to do with the situation. "Airworthiness" is at base a physical property: is the aircraft physically capable of flying safely, is it physically in compliance with its type certificate, etc. An automobile might by physically safe but illegal to drive because its registration is expired; the letter in question similarly says that the aircraft will be illegal to fly if its registration expires. That has nothing to do with whether it is "airworthy" or not.

@randomhead I think you're getting at something important here, and it might be a great demonstration of the FAA's principle of "primacy". I was taught that if the plane failed the AROW check (or any other paperwork check), that it was "not airworthy". I remember asking how an airworthiness determination was anything other than physics-based, and was told "them's the rules". https://www.pilotsofamerica.com/community/threads/bought-a-new-to-me-airplane-registration-is-wrong-still-airworthy.119529/ shows that it's a common-enough viewpoint that even an IA makes the mistake.

@KennSebesta, FYI, I responded to the link above. Gosh, those old coots are worse than us!  (awaiting moderator approval...)

@MichaelHall lol, that's awesome. Good luck!

No.

Does a US state have US-wide airworthiness authority over airplanes registered within that state?

There are two parts to this question - airworthiness and jurisdiction.
AIRWORTHINESS:
14 CFR, Part 3, Subpart A, § 3.5 defines the term airworthy:

Airworthy means the aircraft conforms to its type design and is in a condition for safe operation.

The word is well defined, and has a very specific, and limited in scope meaning that is not applicable in this case.  In other words, it does NOT mean "not legal to fly due to failure to meet a state department of revenue administrative requirement".  It means only what the FAA says it means.  ...Full stop, no ifs ands or buts.
Neither the letter your friend received or the state law regarding registration use the term "airworthy" or any of its derivatives.  Nor does either one hint that failure to register would render the aircraft out of compliance to its type design, or not in a condition for safe operation.
JURISDICTION:
Jurisdiction is a foundational concept of law.  It limits the authority of a legal entity or policy making body to specific geographic borders, and/or subject matters.
The state of Massachusetts does not have "US wide authority" over aviation matters, or really any other function that occurs outside its borders.  No state does, Massachusetts does not claim or even hint that it does, and it is unreasonable to presume otherwise.
You may infer, from the letter you quoted, the following addition in bold:

Our records indicate that your Aircraft Registration in the Commonwealth of Massachusetts is set to expire on December 31, 2023.
If your Aircraft Registration has expired, as the aircraft owner, you cannot legally operate your aircraft [in the Commonwealth of Massachusetts] until you receive your 2024 new registration certificate.

(It was likely omitted in the second paragraph because it is unnecessarily redundant for the general populace.)

In other words, the answer to OP's question is "no" but only because they're asking the wrong question... they mean to ask "Can a US state make it illegal to operate an aircraft" which is not at all the same question as "Can a US state deem an aircraft unairworthy."

Sort of... but who are we to judge the question "wrong"?  (Can a US state make it illegal to do something in other states is also a "wrong" question...)  We can only answer what was asked, and in doing so perhaps point out any fallacies at the root of the question.

@MichaelHall thanks for posting the relevant FAR. That was very helpful in challenging what I was taught long ago by a CFI, which is that noncompliant paperwork equals "unairworthy".

There's a strange pedantry about answering the literal question, but not engaging with the literal source of the question. States cast power outside themselves all the time. For instance, if a driver's license is suspended by the issuing state, all other states agree to honor it. The effect is all that matters to the lay person, not the exact mechanism used. Likewise, when a MA rep says "illegal to fly" that's no different from an MA police officer saying "illegal to drive". Ignoring that with a Dukes of Hazard jump to the next county is done at the pilot's peril.

@KennSebesta, I am sensitive to pedantry and Cliff Clavinism in all forms, and I generally try to avoid it.  (Sure, if someone says "inadvertent IFR" I might quip Oh, you accidently filed an instrument flight plan and picked up a clearance?! but I do it with a twinkle in my eye...)  Anyway, I certainly didn't mean to beat you up on this.  Again, it isn't my definition, it is the FAA's.  Good point about possible reciprocity agreements between the states, or states and the FAA, but pretty sure the "R" in AROW requires Federal Registration, not State.  Maybe a focused follow up question?


text:
What is "Accident" on a VFR sectional?
Seen on the map just north of 2G4 (Garrett Country Airport) is a dot labeled "Accident".

(Direct link to map.)
I never noticed something like that before, and didn't fly close enough to find out what it was. What kind of "accident" is the cartographer trying to draw my attention to? And what kind of accident would have the physical evidence endure for so long as to be a valid data point on the map?

What is "Accident" on a VFR sectional?

It is simply the name of the town.  (Wikipedia link)

PS there is also an incorporated community named "Accident" in Arkansas, but it does not appear on the sectional chart -- https://en.wikipedia.org/wiki/Accident,_Arkansas


text:
Why is the Cirrus Vision SF50's turbine angle so acute?
I saw a Cirrus Jet on the ramp and was struck by how much its engine points upwards. I can't recall having seen this kind of positive thrust angle, and so wondered what the explanation was.
A picture of it in level flight shows that it's not an illusion because of sitting on the landing gear in a funny way. The engine really does have a 10-15degree upwards tilt.

It looks like the exhaust nacelle might be angle a little back to the horizontal, although it's not clear to me if that's a thrust diverter or just allowing expansion of the flow as it exits:

Don't confuse the apparent angle between the intake and exhaust with either engine alignment or thrust vector.  Look at the L1011 or Boeing 727.

There are two questions here: why so and how is it handled.
For the first one, I'll refer to the Jpe61's answer. Basically, it's just a reasonable compromise for a compact single-engine passenger jet.
As for the mitigation part, I happen to know some data.
The engine is mounted 8.53° nose up. This is a bit less than what it visually seems from the nacelle, due to the flattened intake. The engine is partially buried in the fuselage.

From SF50 PIM
The exhaust nozzle is tilted a whopping 14° with respect to the engine centreline (data from FJ33-5A IOI (Installation/Operation Instuctions)). This makes the thrust line pointing 5.47° down, thus overcompensating the engine alignment.

From the same link provided in the Koyovis's answer
As a result, the thrust line passes fairly close to the centre of mass.1 This creates minimal pitch disturbances due to thrust changes. SF50 was created largely for relatively inexperienced first-time jet pilots, and its handling must be fairly straightforward.

1 But still, it seems, slightly higher (esp. with respect to the drag centre). This is somewhat beneficial for speed handling.

Excellent answer. Where do the angle values come from? Service manual?

+1 for this answer

Makes a lot of sense, especially for low speed/high thrust (go around) situation.  Thumbs up for vectored thrust.

@Kenn, mostly from the standard engine and aircraft documentation (I mentioned PIM and IOI). I also have some data from the manufacturer (Cirrus). For the engine, it is interesting to know it is certified only up to 45° roll attitude, and even then only for 30 seconds. (Max 20° roll continuously).

Just as engines fore of the CG are pitched down to create a nose-down pitch torque when thrust is added, rear mounted engines can be pitched up to create the same effect.

adding thrust adds speed, which adds lift, causing the plane to pitch up. Downward pitching thrust moment helps avoid power on stalls by helping to control this tendency,

The angling of the exhaust may have been added to fix an excessive pitching tendency.
One might note the exhaust stream across the tail may have been somewhat unpredictable in design, with either an increase in pitch down due to Coanda effect or a pitch up due to higher pressure in the exhaust stream than surrounding air.  The engineers may have tweaked the exhaust angle to get it just right.
Finally, it should be noted that the angle of the intake is not necessarily directly in line with the combustion chamber and exhaust of the jet.  Indeed, many jets have S-shaped inlets (which may help for birdstrikes).  This is where the line of the nacelle may be a bit deceiving.
Shown here, in this reference, is the actual configuration of the air intake and engine.

It doesn't work that that.  What matters is whether the thrust axis  line passes above, on or below the center of mass for inertial reactions and the vertical aerodynamic center for trim reactions.  The engine could be a mile out front or behind and thrust effects on pitch and trim are the same as long as its attachment to the airframe is rigid.  That engine's thrust axis is made horizontal(ish) because the tailpipe is  curved.  Most of the thrust is generated by the flow accelerating through the nozzle.

I believe the Cirrus uses a technology that Williams calls “EXACT nozzle” which is a thrust vectoring system with no moving parts.

As interesting as that is, it doesn't answer the question about why they mounted the motor that way. Think you can improve the answer?

@KennSebesta well, I keep thinking He 162.  The intake may help reduce fuselage drag, while the compressor/combustor/turbine unit does its job more aligned with the fuse within the nacelle, and the exhaust is angled slightly upwards.  It appears this model borrowed much from its nose mounted prop predecessors, with the jet mount preserving the "look" for their brand loyal customers.

The engine points upwards indeed, but the main question is: how is the thrust vector pointing? If it extends to the Centre of Gravity there will be no pitch moments caused by thrust changes.
Edited photo from this link
The link provided by @RobertDiGiovanni shows the S-bend in the exhaust pipe, which will indeed point upwards from the engine mount axis - the hot exhaust stream needs to be kept away from the aluminium structure.
The thrust axis still looks a bit high to go through the CoG even if horizontal, which won't be much of an issue when considering for instance the low mounted jet engines on an A320.
And on the inclination angle of the engine: on a small aeroplane, where to mount the single jet engine so that the intake is unencumbered, yet the exhaust has a small moment arm relative to the CoG? I reckon they did a pretty good job there.
-----Update-----
@Zeus' answer has a more accurate thrust vector direction, turns out to be even closer to the CoG.

There's an interesting nuance here. While it is true that there's some kind of a reorientation of the stream in the exhaust section, the momentum transfer required to push the airstream up will push the tail down.

BTW, as interesting as that is, it doesn't answer the question about why they mounted the motor that way. Think you can improve the answer?

@KennSebesta The orientation of the engine and that of the exhaust (which determines thrust direction) are two different entities. On a small aeroplane, where to mount the single jet engine so that the intake is unencumbered, yet the exhaust has a small moment arm relative to the CoG? I reckon they did a pretty good job there.

I happen to know "how the thrust vector is pointing", but it was too long for a comment so I wrote a separate answer using the same picture...

As I read it, the question is asking about the engine installation: why is it placed in the way it is?
The reason is overall simplicity. The placement of the engine avoids the need to use ducting or a pylon. If the engine was placed such that it was aligned with the longitudinal axis of the aircraf, it would either need to be installed on a pylon to lift it above the fuselage like in the case of Flaris LAR 1, or it would need to be placed inside the fuselage, necessitating ducting like in the case of Stratos 716X

Flaris LAR1 (image from company website)

Startos 716X (image from company website)
Installing the engine on a pylon rises the thrust vector higher, adding the pitch moment changes due to changes in thrust. Pylon also adds structural weight, as the pylon itself, but also as reinforcements necessary for the fuselage. Installing the engine inside the fuselage adds structural complexity and may complicate the design of the pressure vessel.
While the Cirrus SF50 configuration is the simpliest possible of the feasible single engine applications (installing the engine under the fuselage won't work for a number of reasons), there are two problems with it: thrust vector angle and intake flow stability at high AoA flight.
In the case of Cirrus SF50 the issue with thrust alignment has been tackled by using thrust vectoring: the exhaust is diverted more horizontal as it exits the nozzle. The airflow around the fuselage has obviously been found not to be a critical issue, but whether or not it poses limitations to the operating envelope of the aircraft is not known to me, finding this out would require some research.

The question seems to be about (alleged) thrust angle, not installation.  "Vectored" thrust answers that.  "Airflow around the fuseluge" ... let's say you want more headroom in your cabin?  We know from wings (especially at higher AoA) some flow separation can occur past the apex of the curve.  That's why the intake is mounted there.  Marine creatures have a dorsal fin there for similar reasons:  drag reduction.  Strange but true.  A solid form (such as a winglet) can have less (overall) drag than no tip at all (at  higher AoA).

@RobertDiGiovanni the headline and the first sentence refer "turbine" and "engine".

Perhaps more accurately described as "nacelle".  Anyways, the Flaris LAR1 looks quite similar.  Appreciate your pics.

@RobertDiGiovanni the LAR1 is a good comparison for the SF50, as it portrays "the other" solution for the top-of-fuselage installation. Same concept, different interpretation.

I believe the jetpipe is aligned with the long axis of the aircraft.  Doing this while keeping the engine following the curvature of the fuselage results in the thrust centerline closer to the center of gravity of the aircraft. I suspect this eliminates a lot of undesirable pitch action during throttle changes, similar to that found in Lake amphibious aircraft with the engine mounted high off CG.

If so, then why not mount the tail higher on the body, so that the tail boom would have been flatter on top and the engine would have had fewer bends?

@Kenn Sebesta Probably Wind Tunnel and CFD studies showed such a design would have produced too much drag and added excess weight.

As the engine is tilted, thrust vector is pointed slightly downwards, and as the engine behind the CoG, the engine thrust will induce a pitch moment. I do not know if there is some kind of structure inside the exhaust nozzle to vector the thrust to aligh it more with the longitudinal axis, this might mitigate the pitch moment.

@Jpe61, the nozzle actually even overcompensates the engine tilt and points the exhaust up. I added an answer to illustrate.